The present invention relates to firearm breech bolt assemblies, and more particularly, but not exclusively, to a breech bolt having improved reliability.
Automatic rifles have been standard weapons of choice for the armed forces and police SWAT units. These weapons also have semi-automatic counterparts which are popular with civilians. Many of these automatic and semi-automatic firearms are based on a gas-operated breech bolt carrier system. U.S. Pat. Nos. 2,951,424 and 3,198,076 both to Stoner provide early examples of these types of weapons. Generally, the bolt carrier system of these weapons includes a multi-lug breech bolt that interlocks with lugs on a bolt receiver for firing each round of ammunition. The pressurized gases resulting from the weapon firing a bullet are directed to slide the breech bolt backward and then forward in the receiver, ejecting a spent shell casing and loading a new cartridge from a magazine adjacent the receiver.
Occasionally, the breech bolt becomes misaligned with the receiver when in the bolt is moving forward so the lugs on the breech bolt are no longer aligned with gaps between the lugs on the receiver. When the lugs and gaps slots are out of alignment, the bolt cannot slide forward to chamber the new cartridge and the bolt becomes jammed. Jammed bolts limit the overall reliability of the weapon. By reducing the frequency of jammed bolts, maintenance-actions for the gun are correspondingly reduced and overall reliability is improved. Consequently, there is a need to better ensure the bolt lugs properly mesh with the receiver gaps.